hot spot

hot spot /n./ 1. [primarily used by C/Unix programmers, but
spreading] It is received wisdom that in most programs, less than
10% of the code eats 90% of the execution time; if one were to
graph instruction visits versus code addresses, one would typically
see a few huge spikes amidst a lot of low-level noise. Such spikes
are called `hot spots' and are good candidates for heavy
optimization or hand-hacking. The term is especially used of
tight loops and recursions in the code's central algorithm, as
opposed to (say) initial set-up costs or large but infrequent I/O
operations. See tune, bum, hand-hacking. 2. The
active location of a cursor on a bit-map display. "Put the
mouse's hot spot on the `ON' widget and click the left button."
3. A screen region that is sensitive to mouse gestures, which
trigger some action. World Wide Web pages now provide the
canonical examples; WWW browsers present hypertext links as
hot spots which, when clicked on, point the browser at another
document (these are specifically called hotlinks). 4. In a
massively parallel computer with shared memory, the one location
that all 10,000 processors are trying to read or write at once
(perhaps because they are all doing a busy-wait on the same
lock). 5. More generally, any place in a hardware design that
turns into a performance bottleneck due to resource
contention.